1. Field of the Invention
The present invention relates to a sheet-shaped product of a thermoplastic elastomer. More specifically, the present invention relates to a sheet-shaped product of a thermoplastic elastomer provided with an embossed pattern on the surface thereof, which shows excellent uniform extensibility and emboss (embossed-pattern) retention when it is subjected to secondary forming such as vacuum forming, pressure forming, stamping forming or the like, and which is advantageously used for the skin of automobile parts, furnitures and the like.
2. Background Art
Heretofore, a polyvinyl chloride has been employed as a base material for a sheet for interior automotive trim, which is used for the skin of an instrument panel, a door trim and the like. However, due to the trend toward light-weight automotive parts and in order to meet the demand, from environmental viewpoints, for automotive parts which can be reused or thermally disposed without difficulty, it has begun to put a thermoplastic polyolefin elastomer material (hereinafter may be simply referred to as "TPO") into practical use in recent years.
For example, Japanese Laid-Open Patent Publication No. 1888/1994 discloses a sheet-shaped product based on TPO comprising an olefin copolymer rubber, an olefin copolymer and a crystalline paraffin.
However, the conventional sheet-shaped products of olefin thermoplastic elastomer have the drawback that they show poor extensibility when subjected to secondary forming such as vacuum forming, pressure forming, stamping forming or the like, so that the product with a high draw ratio tends to become torn or become extremely thin.
Further, an embossed pattern is generally provided on the surface of skin materials for interior automotive trim, used for an instrument panel, a door trim and the like so as to impart thereto a leather-like texture. When the conventional sheets made of TPO which are provided, in advance, with such an embossed pattern are subjected to secondary forming such as vacuum forming, debossing (flatting out of the embossed pattern) is likely to occur due to heat applied or deformation caused in the course of the forming process. Thus, there has been a problem in emboss retention. In order to avoid such debossing, a method in which vacuum forming is conducted by using a female metal mold provided with an embossed pattern has been adopted. However, there is still such a problem that only an embossed pattern which is flatter than that of the metal mold is obtained.
It is, therefore, a primary object of the present invention to provide a sheet-shaped product of thermoplastic elastomer which shows excellent uniform extensibility and excellent emboss retension.